Radiant energy signal transmitters are currently being used with public safety vehicles, such as fire and police vehicles, for remotely controlling traffic signals at intersections wherein the signal transmitter is turned on and off at a desired rate. Fire trucks may, for example, use a signal transmitter operating at a frequency that is effective to obtain control of traffic signals at an intersection on a priority basis over the signal provided by a transmitter operating at another frequency that is carried by a police vehicle. Such a multiple priority control system is disclosed in U.S. Pat. No. 4,162,477 to John A. Munkberg.
Such prior radiant energy signal transmitters include a d.c. to d.c. converter, a d.c. storage circuit portion, a triggered radiant energy signaling device, a trigger pulse circuit portion and a trigger pulse timer circuit portion. The d.c. to d.c. converter is energized by the vehicle electrical system to convert the vehicle d.c. voltage to a higher d.c. voltage which is applied to the d.c. storage circuit portion for storage of the d.c. energy. The trigger pulse timer circuit portion provides repetitive signals to a trigger pulse circuit portion, each of such signals causing the trigger pulse circuit to provide a trigger pulse to the triggered radiant energy signaling device to initiate its operation by providing a conductive path for rapid discharge of the d.c. energy stored by the d.c. storage circuit to create a high intensity flash of light. The trigger pulse timers for signal transmitters of this type that are used with systems providing for the remote control of traffic signals at intersections have been manufactured to supply signals at a single rate determined by the priority level of the vehicle with which the transmitter is to be used. Such trigger pulse timers have involved the use of binary counters for obtaining a desired repetition rate.
Such prior radiant energy signal transmitters do not provide a means by which the operator of a vehicle having the radiant energy signal transmitter can change the rate or frequency of operation of such a transmitter to obtain a different operating priority frequency or a frequency of operation that is a non-controlling frequency allowing the radiant energy signal being transmitted to be detected for another purpose or merely to provide a visible radiant energy signal that serves only to make the operators of other vehicles or pedestrians aware of the vehicle having the transmitter. Binary counters as used in the prior transmitters for determining the frequency of operation of the transmitter do not provide for the changing of the operating frequency in a manner that would be accountable to an operator of a vehicle having such a transmitter.